I am stepping in with the response of Neograph734. Google is your friend and you can easily find the answers there.
But I am going to help you. It is easy to be done:
Create a view (page or block) and setup the filter and order criteria to what you want to display. In the pager section, set items to display to 3.
Make an attachment display with the same filter and order criteria. attach the attachment to the first view. Take "attach after" . Then in the pager section, determine how many items you want to show and set the offset to 3.
This way you can either put in the footer section of the first view or the header section of the attachment the text you want to place there.